Now, when you have changed anything with Firebug, rightclick with the mouse on the webpage and use "Bookmark with Scrapbook+" to save the content. You can use "ALT + K" to show the link to your content in the sidebar. Rightclick the url in the sidebar to see the location of your content ("properties"). For example, in my case the content was located at
All files that you have changed with Firebug is stored in that folder. Now, you only have to use FTP or something like that to move the changed files over to your server and you're good to go!